1. Field
The disclosed embodiments relate to elevator systems. More specifically, the disclosed embodiments relate to anti-rotation systems and devices for elevator systems.
2. Related Art
Elevator operation, construction, and maintenance is governed by numerous safety codes and rules. One such code is ANSI A17.1, Safety Code for Elevators and Escalators. In section 2.20.9.8, this code states that “means shall be provided to prevent the rotation of the suspension ropes without restricting their movement horizontally or vertically.” These means are typically known as anti-rotation systems.
A typical anti-rotation system will be explained in a 2:1 elevator cable configuration. FIG. 1 schematically shows a 2:1 elevator cable configuration. The 2:1 elevator cable configuration 100 includes an elevator carriage 110 and a counterweight 120. The elevator carriage 110 and the counterweight 120 are suspended from elevator cables 130, such as steel or composite wound cables.
The cables 130 are each fixed to a cable shackle 140. The cable shackles 140 are configured to extend through and be affixed to a hitch plate 150, 152 disposed on a machine room floor 160. As shown in FIG. 1, a driving motor 170 using the cables 130 and a system of pulleys raises and lowers the carriage 110. It is noted that although the schematic shown in FIG. 1 shows a single cable 130 for simplicity in explanation, such elevator configurations typically comprise a plurality of cables, such as six or more cables.
Typically, the anti-rotation system is implemented as a part of the cable shackles 140. FIG. 2 schematically shows an example of a conventional anti-rotation system. As shown in FIG. 2, the cable shackles 140 include a cable locking mechanism 220 and a threaded rod 210.
The threaded rod 210 extends up from the cable locking portion 220 through the hitch plate 150. The threaded rod 210 is adjusted to an appropriate height by way of, for example, locking nuts (not shown). As a safety precaution, the threaded rod 210 often includes a transverse hole near its top end that is configured to receive a cotter pin (not shown) above the locking nuts.
The cable locking mechanism 220 receives an end of the cable 130. The cable 130 is reversed within the cable locking mechanism 220 and is configured to be wedged therein, locking the cable 130 in place. The cable locking mechanism 220 further includes an aperture 230. The aperture 230 is configured to receive a separate steel cable 240. The cable shackles 140, apertures 230, and the separate steel cable 240 define the conventional anti-rotation system.
Specifically, the steel cable 240 is threaded through each aperture 230 in each cable locking mechanism 220 suspended from the hitch plate 150. Ends of the steel cable 240 are then fastened together with a cable clamp 250 or the like. In this manner, if one of the shackles begins to rotate, the cable 240 will limit the rotation due to the cable 240 being threaded through each of the cable shackles 140.
While the anti-rotation system described above may effectively prevent rotation of the cable shackles, there are a number of drawbacks with the conventional anti-rotation system. As one drawback, as shown in FIGS. 1 and 2, the conventional anti-rotation system is built into the cable shackles 140 and is thus disposed below the hitch plates 150 and 152. That is, the conventional anti-rotation system is disposed within the elevator shaft, and, more specifically, is disposed near the upper end of the elevator shaft. This makes maintenance of the anti-rotation system or other components requiring the removal of the anti-rotation system dangerous and cumbersome to a maintenance person.
For example, during use over time, the cable 240 may become pinched or broken from the shackles 140 trying to rotate, and the cable may need to be replaced. Further, other maintenance or adjustments to the cables 130 or cable shackles 140 may need to take place, requiring removal and replacement of the cable 240 of the anti-rotation system.
However, because the cable 240 is at the top of the elevator shaft and is below the machine room floor 160 and hitch plates 150 and 152, the cable 240 is only accessible through the elevator shaft. Furthermore, in some elevator cable configurations, there may be a substantial amount of clearance, such as twenty feet or more, between the top of the carriage 110 or other platform and where the conventional anti-rotation device is located. As a result, the maintenance person must use an extension ladder on top of the elevator carriage 110 and install safety lines to gain access to the cable shackles 140 and the anti-rotation system. The cable shackles are further in a tight configuration that makes it difficult to remove and install the cable 240, especially when working high up on a ladder that is situated on the top of the elevator carriage 110.
As a result, the prior art design adds to the complexity and time it takes to install or adjust and maintain the elevator cables. This results in additional labor costs. In addition, it places the elevator operator at risk since they must be suspended out over the open elevator shaft to install or adjust the anti-rotation devices on the shackles.
Furthermore, the numerous cables and shackles are in close proximity near the top of the shaft by but under the shift plate 150, 152. To thread the cable through the shackle, while suspended on a ladder, over the open elevator shaft, requires that the elevator technician rotate the cables to align the openings in the shackles to allow the anti-rotation cable 240 through the shackle opening. This is very difficult because the weight of the elevator is suspended by the cable and the cable is very stiff and of a large diameter. As can be appreciated, this aspect of elevator installation and maintenance is a significant drawback.
Accordingly, there is a need for an anti-rotation system that prevents rotation of the shackles while being easily and safely accessed by a maintenance person.